JPH0367042A - Method of controlling vehicle traction by fuel control - Google Patents

Abstract

PURPOSE: To protect a catalyst converter by prohibiting power increase to a cylinder to which fuel is supplied when fuel supply to a desired cylinder is stopped to reduce engine torque for traction control. CONSTITUTION: A brake traction controlling controller 20 starts a brake 26 of a drive wheel through a brake pressure actuator 28 to limit wheel spin when speed by speed sensors 22, 24 indicates an excessively accelerated spin condition in accordance with application of excessive torque to the drive wheel through an engine 10. During this while, the controller 20 gives a traction control active signal to a digital controller 18. The controller 18 selectively sets fuel injection to a fuel injector INJ ineffective, and makes gaseous mixture supplied to an actuation cylinder lean. In a combustion condition of the actuation cylinder, as a result, exhaust quantity of hydrocarbon and carbon monoxide into an exhaust tube 14 can thus be reduced, and such a condition as to cause rapid temperature rise in a catalyst converter 16 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for controlling traction in a vehicle, and more particularly to a method for controlling traction in a port-injection internal combustion engine by disabling selected fuel injectors in the engine. A method includes suppressing fuel from selected cylinders to limit wheel spin.

[Prior Art] A number of methods have been proposed for preventing excessive spin of the drive wheels of a vehicle while the vehicle is accelerating. This excessive spin state is
This occurs when the operator initiates engine torque delivered to the vehicle drive wheels to overcome the frictional forces between the tires and the road surface. These methods include adjusting engine torque and/or adjusting drive wheel braking when an over-accelerated spin condition is detected. As one method of adjusting engine torque output to limit wheel spin during vehicle acceleration (disclosed in U.S. Pat. No. 4,432,430), each fuel injector in a port-injected internal combustion engine is The system is controlled to selectively suppress fuel from the cylinders. This cylinder disabling reduces engine torque output which limits acceleration spin. In this configuration, the fuel-suppressed cylinder draws only air during its intake stroke. This air is discharged into the exhaust system during the exhaust stroke of the cylinder, where it mixes with the combustion gases discharged from the working cylinder into the exhaust system.

In order to minimize the amount of certain exhaust gas components, motor vehicles generally use catalytic converters through which the exhaust gases are discharged to the atmosphere. It is also effective in oxidizing nitrogen oxides and reducing nitrogen oxides. In vehicles where exhaust gases are exhausted to the atmosphere via a catalytic converter, excessive wheel spin is limited by suppressing fuel from one or more cylinders to reduce engine torque output. , the air exhausted from the disabled cylinder into the exhaust system is combined with the combustion by-products of the working cylinder, creating a condition where it is heated to such an excessive level that it can potentially damage the catalytic converter. This is particularly the case when the engine is operated in power enrichment mode, where the air/fuel ratio is high and, as a result, unburned hydrocarbons and carbon monoxide are emitted into the exhaust system. They are mixed with the oxygen-enriched air discharged from the disabled cylinder into the exhaust system. The resulting oxidation of hydrocarbons and hydrogen monoxide increases the temperature of the catalytic converter, creating the potential for excessive temperature conditions.

[Problem to be Solved by the Invention] Accordingly, there is provided a method for protecting a catalytic converter in a vehicle traction control system, the method of protecting a catalytic converter in a vehicle traction control system, which prevents excessive wheel spin by selectively cutting off fuel supply to the engine cylinders. It would be desirable to provide a way to limit torque output.

[Means for Solving the Problems] In order to achieve the present object, the traction control method of the present invention is characterized by the matters specified in the characterizing part of claim 1.

The present invention utilizes a catalytic converter in the exhaust discharge path to control the mixture of air and fuel supplied to the fueled cylinders of a vehicle engine, thereby reducing engine torque to inhibit excessive wheel spin during vehicle acceleration. A method for protecting a catalytic converter from temperature extremes by cutting off fuel supply to selected cylinders of an engine to reduce power output.

In general, the present invention ensures that unburned hydrocarbons do not appear in the oxygen-rich atmosphere of the exhaust gas due to the termination of fuel supply to selected cylinders of the engine for traction control purposes. do.

In one aspect of the invention, power increases to fueled cylinders are inhibited when fueling to any cylinder is stopped to reduce engine torque for traction control.

In another aspect of the invention, the air/fuel ratio of the mixture delivered to the fueled cylinders is increased as the cylinders are selectively defueled to reduce engine torque output.

According to another aspect of the invention, the amount by which the air/fuel ratio is leaned out is a function of the number of cylinders that are disabled by not providing fuel for traction control.

According to yet another aspect of the invention, the amount by which the air and fuel mixture supplied to the activated cylinders is leaned out is a function of engine coolant temperature.

In summary, the present invention reduces the amount of hydrocarbon and carbon oxides that are exhausted from fueled cylinders to the exhaust system and therefore available to combine with excess oxygen that is delivered to the exhaust system from unfueled cylinders. provided for the purpose of

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described by way of example with reference to the following description of preferred embodiments and the accompanying drawings.

With reference to FIG. 1, the present invention will be described as applied to an eight-cylinder internal combustion engine for a vehicle. The internal combustion engine will hereinafter be referred to as engine 1.
It is called 0. In engine 10, each cylinder is supplied with fuel via eight respective fuel injectors INJI-INJ8. This form of fuel exit system is commonly referred to as a port fuel injection system. Air is drawn into the suction manifold 12 of the engine 10 through a suction throttle hole having an operator-controlled throttle that regulates the incoming air to the engine 10 . Air and fuel supplied by the cylinder fuel injector are drawn into the cylinder and combusted. In this way, drive torque is developed and transmitted to the drive wheels of the vehicle. Combustion gas from the cylinder is conventional (three-way)
It is discharged to an exhaust pipe 14 having a catalytic converter 16, and then to the atmosphere. As is known, catalytic converter 1
6 simultaneously converts carbon monoxide, hydrocarbons and nitrogen oxides,
It thereby serves to reduce the release of these ingredients into the population.

Engine 10 is controlled by a conventional digital controller 18. This control includes conventional control of fuel injectors INJ1-INJ8 to inject fuel into each cylinder of engine 10 in time relation to engine rotation. Generally, fuel injectors are controlled in response to various engine and vehicle operating parameters to achieve a predetermined air/fuel ratio. These parameters include engine cooling y & temperature TEMP, manifold absolute pressure MAP.

Throttle position iTP, engine speed RPM, vehicle speed and exhaust oxygen sensor output 02 are included, each of these parameters being provided by a conventional transducer.

Although not shown, digital controller 18 controls other engine/vehicle systems in a conventional manner, including ignition spark timing, vehicle transmission, etc.

Digital controller 18 takes the form of a conventional general purpose digital computer and is programmed to perform various control functions. These control functions include control of fuel injectors INJI-INJ8 to set the desired air/fuel ratio and limit engine torque output for traction control, in accordance with the principles of the present invention and as described below. The digital controller 18 has a read-only memory R
OM.

It is comprised of a random access memory RAM, an analog/digital converter A/D, and an output section I10 that receives discrete signal inputs and provides discrete signal control outputs to, for example, fuel injectors INJ1-INJ8. Generally, under the control of a program stored in ROM, digital controller 18 executes various routines at timed intervals to perform various control functions.

In order to limit acceleration spin of the vehicle drive wheels for traction control, the preferred embodiment of the present invention controls drive wheel braking and engine torque output. Brake control is provided by a conventional brake traction control system having a brake traction control computer 20 responsive to vehicle drive wheel speed via speed sensor 22, non-drive wheel speed provided by speed sensor 24, and the like. The brake traction control computer 20 activates the brake pressure actuator 28 to limit wheel spin when the speed of the speed sensor 22.24 is indicative of an overaccelerated spin condition in response to the application of excessive torque to the drive wheels via the engine IO. The brakes 26 of the drive wheels are actuated via the drive wheel.

Brake traction control computer 20 may take any conventional form including a general purpose digital computer, such as digital computer 18.

Brake pressure actuator 28 may also take any conventional form, such as a DC torque motor responsive to a signal output from brake traction control computer 20 that controls a piston that sets the controlled oil pressure in brake 26. It includes.

It is undesirable to continuously apply significant brake pressure to the drive wheels while the brakes 26 are operating to limit wheel spin. For example, applying the brakes for extended periods of time to limit wheel spin during high engine torque output conditions can result in the brakes 26 heating beyond acceptable levels. To prevent this condition, engine torque output is limited when traction control requires limiting wheel spin by selectively disabling fuel injection to one or more cylinders of engine 10. By suppressing fuel from the cylinder,
The cylinder only sucks air, but does not operate to generate torque to drive the drive wheels. The air drawn into the cylinder is exhausted into the exhaust pipe 14 during the exhaust stroke.

Generally, a traction control active signal is provided by brake traction control computer 20 to digital controller 18 indicating that wheel spin is being limited by activation of brakes 26 in response to a detected overspin condition. The digital controller 18 ( 1(raa
+p) selectively disable fuel injection to the cylinders one by one. Upon termination of the traction control active signal from the brake traction control computer 20 indicating recovery from an overspin condition, the disabled cylinders are activated one after the other.

As previously mentioned, when fuel is suppressed from one or more cylinders of the engine lO, these cylinders direct air to the exhaust pipe lO.
Discharge within 4 days. This creates exhaust gas conditions that will result in a rapid temperature rise in the catalytic converter 16. This condition is due to oxygen in the air exhausted into the exhaust pipe 14 and non-flammable hydrocarbon or carbon monoxide gases exhausted from the fueled cylinder. This condition is amplified when the cylinder is disabled, resulting in an increase in the amount of hydrocarbons emitted into the exhaust pipe 14 due to the oxygen and gas from the disabled cylinder.
is in power increase (povcr cnrjcbment). In accordance with the present invention, the digital controller 18 protects the catalytic converter 16 when the cylinders are selectively disabled by leanening the mixture supplied to the working cylinders. By making the air-fuel mixture leaner, the combustion conditions in the working cylinder result in reduced emissions of hydrocarbons and carbon oxides into the exhaust pipe 14, leading to a rapid temperature rise in the catalytic converter 16. prevent.

2A and 2B, a routine for selectively activating and disabling cylinders of traction controlled engine 10 is shown. This routine is executed repeatedly at selected intervals, such as 100 milliseconds.

The ROM of the digital controller 18 is shown in FIG.
Contains the instructions necessary to develop the algorithm shown in Figure B.

When explaining the functions of algorithms encoded in ROM, references to tasks detailed in functional blocks of flowcharts are indicated by "nn", where nn is the text of the same functional block of the specific flow being referenced. The diagram does not represent the actual ROM commands.It is recognized that the diagrams are not representative of the actual ROM commands.It is recognized that the flowcharts are available to those skilled in the art to construct the actual commands necessary to accomplish the tasks described in the text of the same functional blocks. There are a variety of known information processing languages that are possible.

FIG. 4 shows the routine operations of FIGS. 2A and 2B in controlling the torque output of engine 10 for traction control. Brake traction control computer 20
Whenever the traction control active signal from is transitioned from not active to active, the number of activated cylinders is decreased by one after an initial delay tl, eg, 3 seconds. If the traction active indicator is subsequently continuously active, cylinders are further disabled at the rate of one every t2 seconds (also every 3 seconds) until a minimum of 4 cylinders is reached. . Traction control active signal goes from active to knot
Whenever going active, the number of activated cylinders is increased by one after an initial delay t, for example 1 second. 1. If the traction active indicator continues to be inactive thereafter, a cylinder is further activated every t4 seconds (every 161 seconds) until all eight cylinders are reached.

When the traction control routine of FIG. 2A is entered <30>, traction control is disabled and the traction control active flag is assumed to be reset <32>. The routine then determines whether traction control is active by sampling the traction control active or inactive signal from brake traction control computer 20 (34).

If the traction control signal from brake traction control computer 20 indicates that traction control is active, the routine indicates that traction control is active by setting a traction control active flag <36>.

If the delay has not yet ended, the program then decrements the cylinder disable delay td <38°40>. This delay period is time t1 or t2 in FIG. 4, which, as previously discussed, is the time imposed before disabling the first or subsequent cylinder.

The routine then increases the cylinder increment delay, t, if the delay has not yet ended <42.44>.

This delay period is time t or t4 in FIG.
As mentioned above, this is the time imposed before the first or subsequent cylinders are activated.

First, traction control is not active (46)
, and was also inactive the last time the traction control routine of FIG. <52> is in 8 cylinder mode.

In this case all cylinders are activated and the program exits the routine. This is routine normal operation during normal non-regulated engine operation.

All of the above steps are repeated until there is a time such that a traction control active signal is provided by brake traction control computer 20 indicating an over-accelerated spin condition. If this time exists, the traction control active flag is set <36>
. This condition is detected next <46>. The program proceeds to disable engine 10 cylinders one by one based on the aforementioned time criteria until up to four cylinders have been disabled or until the traction control active signal expires. If traction control was not active during a previous run of the routine but is currently active <54>, the cylinder disable delay t, is set to the initial delay value tl shown in FIG. 4 <56>. Once set, the program detects that the period td has not been completely reduced in step 40 and proceeds to set the minimum number of cylinders that must be activated.
60〉. This lower limit on the number of cylinders activated for engine operation may be set by parameters such as, for example, engine coolant temperature, engine speed, rate of change of throttle position, or transmission shift status. The foregoing steps are repeated until the end of the initial delay tl, the engine is maintained in eight cylinder mode, and the program exits the routine <52>.

Once the initial delay period tl has been completely reduced <38>, the program checks <82> to determine whether the number of fueled cylinders has been reduced to a minimum value (4 in this example). If not reduced to that extent, the number of fueled cylinders is reduced by one <64)
, the cylinder reduction delay td is set to time t2 shown in FIG. 4 <66>.

As mentioned above, this time is the delay imposed during the reduction of the number of activated cylinders after the initial delay t1.

As implemented on each execution of the routine, the number of activated cylinders is limited to a minimum value <60> based on the most recent engine/vehicle operating conditions. When the mode is 8 cylinders or less,
The power increase delay t is initialized to a value that represents the period of time after all e cylinders are reactivated and before the power increase is rambled 〈68〉. As mentioned above, this is to protect the catalytic converter 16. The fuel to the fuel injector of cylinder number 8 is I1 for that cylinder's fuel injector.
It is disabled by applying a zero pulse to the 0 output port.
7o〉. Since the number of cylinders has been reduced only once, the system is in 7 cylinder mode <72> and the program exits the routine.

As long as traction control control is active〈46〉
, cylinders are disabled up to a lower limit of 4 cylinders at a time at intervals of t2 seconds <58.82.84°66>. If the number of activated cylinders is less than or equal to 6 <72>, the fuel injector of cylinder number 5 is further disabled <74>. If the number of activated cylinders is less than or equal to 5 <76>, the fuel injector of cylinder number 3 is further disabled <78>. If the number of activated cylinders is 4 <80>, the fuel injector of cylinder number 2 is further disabled <82>. Steps 48.54-58
If the number of cylinders corresponding to the mode set in and 62-66 is disabled due to lack of fuel supply, the program exits the routine.

When the traction control active signal is terminated by the brake traction control computer, indicating recovery from an overspin condition, the number of initially coupled cylinders is increased.

When the traction control active signal is terminated, the routine determines that traction control is inactive <32.34.36>. This condition is then detected <48> and the program continues to run the engine on the aforementioned time basis until all eight cylinders are activated or until the traction control active signal occurs again.
Proceed to activate the 0 cylinders one by one. If traction control was active during the previous routine execution period but is now inactive <48>, the cylinder increase delay t, is set to the initial delay value t3 shown in FIG. 4 <84>. This time is reduced with each execution of the traction control routine <42.44>
, while it has not elapsed <86>, the lower limit of the number of cylinders is set <60>, and the fuel injector is disabled according to the number of activated cylinders <52.88-82>.

Once the initial delay J(lII) t3 has been completely reduced to zero <44>, the program checks <50> to determine whether the number of fueled cylinders has been increased to eight. If not, increase the number of activated and fueled cylinders by one;
88°°, the cylinder deposition delay t1 is the time t shown in FIG.
Set to 4〈9o〉.

Thereafter, the cylinders are disabled as described above according to the operating mode set in steps 46-50 and 84-9o <52.68-82>. The foregoing steps are repeated <50> until all cylinders are activated and the routine establishes eight cylinder mode <52>.

In summary, the brake traction control computer 2
When the traction control active signal from zero transitions from not active to active, the number of activated cylinders of engine 10 is decreased by one after an initial delay t1. If the traction control active signal remains active thereafter, additional cylinders are disabled at a rate of one every t2 seconds until the minimum number of four cylinders is achieved.

Whenever the traction control active signal transitions from active to not active, the number of activated cylinders is increased by one after an initial delay of 13 seconds. If the traction control active indicator remains inactive thereafter, an additional cylinder is activated every t4 seconds until all eight cylinders are activated again.

The pulse width of the signal energizing the fuel injectors INJI-INJ8 is determined in a conventional fuel control routine to set the desired air/fuel ratio in response to the calculated amount of air drawn into each cylinder. Control of fuel injectors INJI-INJ8 in time relationship with engine 10 may take any conventional form.

However, in accordance with the principles of the present invention, the fuel supply to the cylinders is shut off to reduce engine torque output, thus
As mentioned above, in order to prevent excessive temperature rise in the catalytic converter 16, the fuel injectors INJI-INJ
The scheduled or calculated operating air-fuel ratio used when calculating the pulse width for energizing the 8 is adjusted.

FIG. 3 shows a routine for calculating the air/fuel ratio used in the fuel control routine to set the pulse width for the fuel injector of the cylinder being fueled. Referring to FIG. 3, the normal operating air-fuel ratio is first calculated <92>, and then this normal operating air-fuel ratio is calculated as lean out (lean out).
) (rise) to determine the amount. In this example, the normal operating air/fuel ratio increase is a function of the number of cylinders that are not fueled for traction control. Furthermore, the amount by which the air/fuel ratio is leaned out is a function of coolant temperature.

The amount of lean-out is predetermined and set to prevent the temperature of the catalytic converter 16 from increasing excessively, thereby ensuring reliable operation.

Generally, if the system is not operating in eight cylinder mode, indicating that fuel is being withheld from at least one or more cylinders of engine 10 <94>, a particular mode of operation is determined. If operating in 7-cylinder mode, the traction control lean-out air/fuel ratio values for the 7 fueled cylinders are calculated as a function of cooling branch temperature by the system constructed from a look-up table for the 6 cylinders. When operating in mode <100>, the traction control leanout air/fuel ratio values for the six fueled cylinders are obtained from the lookup table as a function of coolant temperature <102>. When the system is operating in 5 cylinder mode <104>, the value of the traction control leanout air/fuel ratio for the 5 fueled cylinders is obtained from the lookup table as a function of temperature <1
06>. Finally, if the program determines that the system is operating in 4-cylinder mode <104>, the values of the traction control lean-out air/fuel ratios for the four fueled cylinders are determined as a function of temperature. <108> obtained from the collation table. The traction control lean-out air-fuel ratio obtained from the look-up table depending on the cylinder operating mode is added to the operating air-fuel ratio determined in step 92 <110> to lean out the operating air-fuel ratio. Digital controller 18, running a fuel control routine, uses the lean-out operating air-fuel ratio to control engine 1.
determining the pulse width applied to the working fuel injector at the working cylinder and setting the air-fuel ratio of the mixture at the working cylinder to this determined lean-out air-fuel ratio;

Following termination of the traction control active signal provided by the brake traction control computer 2o, when the number of activated cylinders is returned to eight, the power increase delay initialized in step 68 of FIG. <112.114> is timed with 94> when the mode is detected. If the delay has not yet elapsed, the program exits the routine but no power increase is activated. However, the power increase delay period has not passed yet.
2>, if the conditions for power increase exist <116>,
The power increase air-fuel ratio, which is dependent on engine operating conditions, is subtracted from the operating air-fuel ratio to enrich the mixture for power increase <118>. The program then exits the air/fuel ratio control routine. <11 if no power increase condition exists
6>, step 118 is bypassed and the program exits the routine.

The air-fuel ratio set in the routine of FIG. 3 is used by the digital controller 18 in the normal fuel control routine to set the air-fuel ratio of the air-fuel mixture supplied to the fuel-supplied cylinders of the engine 10 to a desired ratio.

As mentioned above, this ratio maintains protection of the catalytic converter 16:
+T, which is done by lean-out the mixture depending on the number of disabled cylinders and by inhibiting power increases while a cylinder is disabled. , and by not providing fuel to selected cylinders during the period after all cylinders have been activated following engine torque control.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a general form of a vehicle traction control device for a port fuel injection internal combustion engine. 2A, 2BIJ, and 3 are flow diagrams illustrating the operation of the digital controller of FIG. 1 in controlling an engine for traction control in accordance with the principles of the present invention. Figure '1lfsJ is a diagram showing selective disabling of the cylinders of the engine for traction control shown in Figure 1. lO...Engine 16...Catalytic converter 18...Digital controller 20...Brake traction control computer 22
, 24...Speed sensor 28...Brake pressure actuator (4 other people)

Claims (1)

[Scope of Claims] 1. A traction control method for a vehicle having wheels driven by an engine (10), the engine having a plurality of cylinders into which air is taken in, and a fuel injector (INJI-) for each cylinder. INJ8), the cylinder is configured to send fuel to the cylinder to be mixed with the air sucked into the cylinder, and thus set a predetermined air-fuel ratio of the air-fuel mixture in the cylinder. The control method includes the step of: (20) detecting an overaccelerated spin condition of a drive wheel; and when the overaccelerated spin condition is detected so as to be able to recover from the overaccelerated spin condition;
disabling (18, FIG. 2) the injection of fuel from selected fuel injectors to control fuel from each cylinder to reduce the engine torque output driving the wheels; the fuel injectors of are activated to deliver fuel to their respective cylinders and set a scheduled air-fuel ratio, (A) determining a normal operating air-fuel ratio (92);
(B) When fuel is being held back from the remaining cylinders,
so that the air/fuel ratio of the mixture in the cylinder corresponding to the activated fuel injector leans out from the normal operating air/fuel ratio.
When disabling fuel injection from a selected fuel injector, the determined normal operating air-fuel ratio is increased (94-11
0) A traction control method characterized by setting a planned air-fuel ratio value. 2. The method of claim 1, wherein the determined normal operating air/fuel ratio increase is a predetermined function of the number of selected fuel injectors whose fuel injection is disabled. 3. The method of claim 2, wherein the determined normal operating air/fuel ratio increase is also a predetermined function of engine temperature. 4. Reactivating fuel injection from the selected fuel injector when the detected over-acceleration spin condition of the drive wheels ends, the step of setting: (A) a normal operating air-fuel ratio; (B) detecting a power increasing operating condition of the engine, and reducing the determined normal operating air-fuel ratio by a predetermined power increasing amount when the engine power increasing operating condition is detected; a predetermined power increase amount for a predetermined normal operating air-fuel ratio while fuel from the selected fuel injector is disabled and for a predetermined period following reactivation of fuel injection from the selected fuel injector; Prohibit the decrease of (
D) When fuel is being controlled from the remaining cylinders, the air/fuel ratio from the selected fuel injector is such that the air/fuel ratio of the cylinder corresponding to the activated fuel injector leans out from the normal operating air/fuel ratio. 4. A method according to any one of claims 1 to 3, comprising the step of setting the value of the scheduled air-fuel ratio by increasing the determined normal operating air-fuel ratio while fuel injection is disabled. .